Malnutrition Accelerates Colorectal Cancer Progression through Macrophage Activated by B Cells Immune via Gut Microbiota

Abstract Background: Malnutrition threatened the clinical outcomes of colorectal cancer (CRC) by reducing patients’ responses to anti-cancer treatments and ultimately shortening thesurvival time. Recently malnutrition has been confirmed to play an important role in CRC progress via gut microbiota. However, roles of gut microbiota in the immunopathogenesis of malnutrition and its underlying mechanisms remain inconclusive. Methods: Patient-Generated Subjective Global Assessment (PG-SGA) was performed to determine the nutrition status in colon cancer patients. 16srRNA sequencing was prepared to explore the dramatic variation of the fecal microbiota among patients with different nutrition status. Fecal microbiota transplantation was used to transplant into C57BL/6J mice model and DSS/AOM mice model. Immunohistochemistry and immunofluorescence were applied to test the CD makers. Fluorescence-activated cell sorting was also prepared to explore the B cells and macrophage from serum and tissues. Enzyme-linked immunosorbent assay and qPCR were used to determine the expression level of cytokines.Results: In this work, we found the specific microbiota species including Atopobium.vaginae, Selenomonas.sputigena and Faecalibacterium.prausnitzii, which may be considered as the diagnostic biomarkers to help improve poor prognosis in CRC. These microbiota were found to be protumorigenic and adversely affect the nutritional status and overall survival of the animal models. More importantly, our evidence suggesting that these fecal microbiota recruited B cells and macrophage to activate the specific tumor immune in CRC. Depletion of B cells significantly suppressed fecal microbiota induced-M2b polarization, as well as the protumorigenic activity of tumor-associated macrophages in vivo.Conclusion: gut microbiome in CRC under malnutrition status could upregulate the activity of B cells and protumorigenic macrophage in CRC. Gut microbiome intervention could be a feasible approach to malnutrition-related CRC treatment.